This invention is an improved process for producing poly (vinyl acetals). All known practices for the production of poly (vinyl acetal) consist of combining a poly (vinyl alcohol) with an aldehyde in the presence of added catalyst.
U.S. Pat. No. 1,990,399 describes the production of poly (vinyl acetal) in a one phase batch process using aqueous hydrochloric acid as a catalyst and solvent. Separate feedstocks of poly vinyl alcohol) and aldehyde are added.
Another process for the production of poly (vinyl acetals) described in U.S. Pat. No. 2,545,683, involves a condensation reaction between poly (vinyl alcohol) or a partially hydrolyzed ester of poly (vinyl alcohol) and a class of reactants called Shiff bases. These Shiff base reactants are prepared by the condensation reaction of a primary amine with an aromatic ketone.
Other methods producing poly (vinyl acetals) include U.S. Pat. No. 2,487,864 and U.S. Pat. No. 2,513,189 which describe condensation reactions between poly (vinyl alcohol) and aldehyde taking place in a water-containing polar solvent in the presence of an acid catalyst.